A variety of storage racks have been designed to store tools, equipment, merchandise, and other items. Certain storage racks comprise horizontal shelf panels that are supported by a frame which, in turn, is supported by generally vertical corner support posts. Each shelf frame is formed by front and rear cross-beams and side beams which are attached at their ends to the corner support posts. A solid panel, e.g., particle board, metal panel, or the like is mounted on or within the frame.
Large storage racks having a span or width of 96 inches or greater and which can handle heavy loads, e.g., 3,000 pounds or more typically have cross-beams with added clips or flanges with inwardly extending lances that engage wedge-shaped slots in corner support posts. Such cross-beams are expensive to manufacture and tend to be heavy, resulting in increased shipping costs. Such a cross-beam design is shown, for example, in U.S. Patent Application Ser. No. 61/050,992, the disclosure of which is incorporated herein by reference. U.S. patent application Ser. No. 11/854,500, the disclosure of which is incorporated herein by reference, describes certain storage racks having shelves about 48 inches long and about 18 inches wide can support 1500 pounds per shelf. These racks have corner posts 1, with a standard boltless post design as shown in FIG. 1. The posts are Cold Roll steel and typically 20-gauge. As shown in FIGS. 2a-2c, cross-beams 2 have a “Z-style” cross sectional configuration and are made of 16-gauge Hot Rolled (P&O) steel according to ASTM A1011-CS Type B (Rockwell Hardness of 75 or less) or Cold Roll steel or ASTM A1008 commercial steel. With particular reference to FIG. 2c, these Z-style cross-beams include a generally vertical upper wall 12, a generally horizontal support wall 14 extending inwardly from the lower edge of the upper wall, an angled intermediate wall 16 that extends downwardly and outwardly from the inner edge of the generally horizontal wall and a lower wall 18 that extends it downwardly from the outer edge of the angled wall. The cross-beam is made of a single sheet of steel folded into the indicated cross-sectional configuration which has an overall width of 2 3/32 inches. The width of the upper wall 12 is about 9/16 inch. The width of the horizontal wall 14 is 9/16 inch, the width of the angled intermediate wall 16 is about 27/32 inch. The angle of the intermediate wall 16 to the horizontal wall 14 is about 54°. The width of the lower wall 18 is about 17/32 inch. The lower wall 18 is generally vertical and lies in generally the same plane as that of the upper wall 12. At each end of the cross-beam, a rivet 30 extends outwardly from the upper wall 12 and a rivet 32 extends outwardly from the lower wall 18.
In one known storage rack, the length of the front and rear cross-beams is about 48 inches and the length of the side cross-beams is about 18 inches. The cross-beams 2 have the Z-styled cross-sectional configuration as described above and are attached at their ends by boltless connections, i.e., rivets 30, 32 extending from the ends of the cross-beams 2 into keyhole slots 3 in upright corner support posts 1, and are seated in those slots 3. The corner support posts 1, 1A may be of the standard type shown in FIG. 1 or, as show in FIGS. 2a and 2b, may have concealed slots 3.
The cross-beams 2 are arranged to form frames for a shelf panel, preferably made of ⅝ inch thick (or ½ or 10 mm or 16 mm) particle board or the like. Each panel is made of commercial grade particle board having a density of about 40-45 pounds per cubic foot (“lb./cf”) and preferably about 42 lb./cf. In this arrangement, each shelf is capable of supporting a weight of 1,500 pounds as measured according to ANSI MH28.1-1977, modified as described below. ANSI Standard MH28.1-1977 states:
6.2 Determination by Test                6.2.1 The location of test loads along the shelf and perpendicular to it shall simulate uniformly distributed loading. End connections (clips, rivets) shall be those used in the finished sections.        
For testing purposes, the section shall consist of two upright assemblies not bolted to floor. A test shelf shall be installed and fully seated into the section, and additional shelves may be installed above and below the test shelf, as required, for section stability. Weight of (not to exceed) 25 lbs increments is equally spaced on test shelf with a minimum gap of ¼″ in between to prevent a bridging effect.                6.2.2 After proper installation, preload shelf to 50 lbs to set clips and structure. Remove load and set gauges to zero. An initial uniform load equal to 50% of expected rated uniform design load or 50% of allowable deflection (SPAN/140) shall be applied. Loads or deflections shall then be increased in maximum increments of one-tenth of the expected failure load or deflection.        6.2.3 The allowable rated uniform load derived from test results shall be the smallest of the following:        (a) Two-thirds (factor of safety of 1.5) of the ultimate average failure load carried by the shelf.        (b) Eight-tenths (factor of safety of 1.25) of the average load at which the load deflection curve becomes nonlinear (yield point).        (c) The load at which the maximum vertical deflection (width or depth), including deformations in end connections, equals the effective shelf width or depth (span) divided by 140, measured at the center of the edge with respect to the position of the same point of the shelf at the beginning of the test.        (d) Four times the capacity of the shelf connection as defined in section 8.2.1 (factor of safety of 2).        
6.3 Test data evaluation                6.3.1 Where practicable, evaluation of the test results shall be made on the basis of the average values resulting from tests of not fewer than three identical specimens, provided the deviation of any individual test result from the mean value does not exceed ±10%. If such deviation from the mean value does exceed 10%, at least three more tests of the same design shall be made. The average of all tests shall then be regarded as the result of the series of tests and used as the value from which the rated uniform load is derived.        6.3.2 Once the rated uniform load has been determined as specified above, the following additional tests shall be made using a properly installed new set of specimens. An initial load of 50% of the design load shall be applied to the shelf. Return to 5% of the designed load and set dial indicators at zero. Apply 125% of design load and hold for 15 minutes. Return to 5% design load and take readings. The maximum permanent set must be equal to or less than 0.15 L/140.        
The shelf load of the storage rack having the Z-style cross-beams of U.S. patent application Ser. No. 11/854,500 was tested as described in ANSI MH28.1-1977 over a 24 hour period. Initially, 100 pounds (from 25 pound bags of lead shot) were distributed evenly by hand over the shelf. Then, every two hours 100 pounds (four 25-pound bags of lead shot) is added to about half of expected capacity, e.g., 1500 pounds. A dial meter was placed under the shelf to measure deflection. The load, i.e., about half of expected capacity, was allowed to sit on the shelf for 35-40 minutes. Then, 100 pound increments (from 25-pound bags of lead shot) were added up to the capacity, i.e., when the allowable deflection (SPAN/140) has been met. The load was then allowed to remain on the shelf an additional 24 hours to assure that no failure occurred during that period.